<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>图案生成-重复图案</title>
</head>
<body>
    <canvas width="512" height="512"></canvas>

    <script src="/common/lib/gl-renderer.js"></script>
    <script type="module">
        /**
         * gl-renderer用法
         * 1.创建renderer对象
         * 2.创建webgl程序
         * 3.设置uniform变量
         * 4.设置缓冲区数据
         * 5.渲染
         * 
         * */ 

        //  1.
         const canvas = document.querySelector("canvas");
         const renderer = new GlRenderer(canvas);

        // 2.
        const vertex = `
            attribute vec2 a_vertexPosition;
            attribute vec2 uv;
            varying vec2 vUv;
            
            void main() {
                gl_PointSize = 1.0;
                vUv = uv;
                gl_Position = vec4(a_vertexPosition, 1, 1);
            }
        `;
        const fragment = `
            #ifdef GL_ES
                precision mediump float;
            #endif

            varying vec2 vUv;
            uniform float rows;
            
            void main() {
                vec2 st = fract(vUv * rows);
                float d1 = step(st.x, 0.9);
                float d2 = step(0.1, st.y);
                gl_FragColor.rgb = mix(vec3(0.8), vec3(1.0), d1 * d2);
                gl_FragColor.a = 1.0;
            }
        `;

        const program = renderer.compileSync(fragment,vertex);
        renderer.useProgram(program);

        // 3.
        renderer.uniforms.rows = 32;

        // 4.
        renderer.setMeshData([{
            positions:[
                [-1, -1],
                [-1, 1],
                [1, 1],
                [1, -1],
            ],
            attributes:{
                uv:[
                    [0, 0],
                    [0, 1],
                    [1, 1],
                    [1, 0],
                ]
            },
            cells: [[0, 1, 2], [2, 0, 3]],
        }]);

        // 5.
        renderer.render();

    </script>
</body>
</html>